linux-kernel - Re: [PATCH] audit: add arch field to seccomp event log

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Message-ID: <1392756919.2165.34.camel@flatline.rdu.redhat.com>
Date:	Tue, 18 Feb 2014 15:55:19 -0500
From:	Eric Paris <eparis@...hat.com>
To:	Richard Guy Briggs <rgb@...hat.com>
Cc:	linux-audit@...hat.com, linux-kernel@...r.kernel.org,
	Steve Grubb <sgrubb@...hat.com>
Subject: Re: [PATCH] audit: add arch field to seccomp event log

On Tue, 2014-02-18 at 15:50 -0500, Richard Guy Briggs wrote:
> On 14/02/14, Eric Paris wrote:
> > On Fri, 2014-02-14 at 15:52 -0500, Richard Guy Briggs wrote:
> > > On 14/02/14, Richard Guy Briggs wrote:
> > > > On 14/02/14, Eric Paris wrote:
> > > > > On Fri, 2014-02-14 at 15:23 -0500, Richard Guy Briggs wrote:
> > > > > > The AUDIT_SECCOMP record looks something like this:
> > > > > > 
> > > > > > type=SECCOMP msg=audit(1373478171.953:32775): auid=4325 uid=4325 gid=4325 ses=1 subj=unconfined_u:unconfined_r:unconfined_t:s0 pid=12381 comm="test" sig=31 syscall=231 compat=0 ip=0x39ea8bca89 code=0x0
> > > > > > 
> > > > > > In order to determine what syscall 231 maps to, we need to have the arch= field right before it.
> > > > > > 
> > > > > > To see the event, compile this test.c program:
> > > > > > 
> > > > > > =====
> > > > > > int main(void)
> > > > > > {
> > > > > >         return seccomp_load(seccomp_init(SCMP_ACT_KILL));
> > > > > > }
> > > > > > =====
> > > > > > 
> > > > > > gcc -g test.c -o test -lseccomp
> > > > > > 
> > > > > > After running the program, find the record by:  ausearch --start recent -m SECCOMP -i
> > > > > > ---
> > > > > >  kernel/auditsc.c |    1 +
> > > > > >  1 files changed, 1 insertions(+), 0 deletions(-)
> > > > > > 
> > > > > > diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> > > > > > index 6874c1f..c464d44 100644
> > > > > > --- a/kernel/auditsc.c
> > > > > > +++ b/kernel/auditsc.c
> > > > > > @@ -2412,6 +2412,7 @@ void __audit_seccomp(unsigned long syscall, long signr, int code)
> > > > > >  		return;
> > > > > >  	audit_log_task(ab);
> > > > > >  	audit_log_format(ab, " sig=%ld", signr);
> > > > > > +	audit_log_format(ab, " arch=%x", current->audit_context->arch);
> > > > > 
> > > > > 
> > > > > What happens if the task does not have current->audit_context allocated?
> > > > > Seems possible if signr is non-zero...
> > > > 
> > > > I had assumed that since we got this far, that there was an audit
> > > > context.  This was my first patch:
> > > 
> > > Sorry, pulled the trigger too fast:
> > > 
> > > ---
> > >  kernel/auditsc.c |    6 ++++++
> > >  1 files changed, 6 insertions(+), 0 deletions(-)
> > > 
> > > diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> > > index 6874c1f..3023d03 100644
> > > --- a/kernel/auditsc.c
> > > +++ b/kernel/auditsc.c
> > > @@ -2406,12 +2406,18 @@ void audit_core_dumps(long signr)
> > >  void __audit_seccomp(unsigned long syscall, long signr, int code)
> > >  {
> > >         struct audit_buffer *ab;
> > > +       struct audit_context *context audit_get_context(current, 0, 0);
> > 
> > missing '='   but this isn't what audit_get_context() does...   it's
> > crappy naming...    I'd think a combo of audit_dummy_context() and
> > current->audit_context would be most appropriate.
> 
> Ok.  I think I finally understand audit_dummy_context().  Thanks for the
> hint.  However, it appears it is not useful in this sitation, since if
> there is an audit_context, even a dummy context, it appears arch is
> filled in.

get a good commit message and feel free to add my Acked-by.

-Eric
> 
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> @@ -2406,12 +2406,18 @@ void audit_core_dumps(long signr)
>  void __audit_seccomp(unsigned long syscall, long signr, int code)
>  {
>  	struct audit_buffer *ab;
> +	struct audit_context *context = current->audit_context;
>  
>  	ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_SECCOMP);
>  	if (unlikely(!ab))
>  		return;
>  	audit_log_task(ab);
>  	audit_log_format(ab, " sig=%ld", signr);
> +	audit_log_format(ab, " arch=");
> +	if (context)
> +		audit_log_format(ab, "%x", context->arch);
> +	else
> +		audit_log_format(ab, "(null)");
>  	audit_log_format(ab, " syscall=%ld", syscall);
>  	audit_log_format(ab, " compat=%d", is_compat_task());
>  	audit_log_format(ab, " ip=0x%lx", KSTK_EIP(current));
> 
> - RGB
> 
> --
> Richard Guy Briggs <rbriggs@...hat.com>
> Senior Software Engineer, Kernel Security, AMER ENG Base Operating Systems, Red Hat
> Remote, Ottawa, Canada
> Voice: +1.647.777.2635, Internal: (81) 32635, Alt: +1.613.693.0684x3545


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